Hydroprocessing can include processes which convert hydrocarbons in the presence of hydroprocessing catalyst and hydrogen to more valuable products.
Hydrotreating is a hydroprocessing process used to remove heteroatoms such as sulfur and nitrogen from hydrocarbon streams to meet fuel specifications and to saturate olefinic or aromatic compounds. Hydrotreating can be performed at high or low pressures, but is typically operated at lower pressure than hydrocracking.
Hydrocracking is a hydrocracking process in which hydrocarbons crack in the presence of hydrogen and hydrocracking catalyst to lower molecular weight hydrocarbons. Depending on the desired output, the hydrocracking reactor may contain one or more beds of the same or different catalyst. Hydrocracking is a process used to crack hydrocarbon feeds such as vacuum gas oil (VGO) to diesel including kerosene and gasoline motor fuels.
Fluid catalytic cracking (FCC) is the predominant source of gasoline production in many refineries as the result of cracking heavier, less valuable hydrocarbon feed stocks such as VGO. The FCC unit comprises a reactor that is closely coupled with a regenerator, followed by downstream hydrocarbon product separation. Hydrocarbon feed contacts catalyst in the reactor to crack the hydrocarbons down to smaller molecular weight products. During this process, coke tends to accumulate on the catalyst which is burned off in the regenerator.
Light cycle oil (LCO) is produced in an FCC unit and can be withdrawn as a side stream from the FCC main fractionation column. LCO is a dealkylated aromatic typically comprising two aromatic rings. LCO can be directed to the diesel pool but it may degrade the quality of the diesel pool due to its high aromaticity and low cetane value. Heavy cycle oil (HCO) is an FCC liquid stream pumped around to cool the main fractionation column but is not often recovered from the main fractionation column.
Straight run diesel (SRD) is a hydrocarbon stream boiling in the diesel boiling range that is provided by distilling crude oil in a crude fractionation column and taken as a side stream from the crude column.
There is a need, therefore, for improved processes and apparatuses for processing diesel and LCO together but that preserve or boost cetane of the blended diesel stream.